The number of weather-related disasters has quadrupled over the past 20 years and the world should do more to prepare for them, the aid agency Oxfam says.

Population increases mean more people are affected when catastrophic weather events take place, it says in a report.

Global warming is to blame for the growing number of weather disasters, Oxfam adds.

An average of 500 such disasters are now taking place each year, compared to 120 in the 1980s, the report says.

The number of floods has increased six-fold over the same period.

Small disasters ignored

The agency expresses particular concern about the increase in small and medium-sized weather events, which it says affect great numbers of people, but do not attract as much international aid as large, well-publicised natural disasters.

The report argues that climate change is responsible for the growing number of weather-related disasters - more intense rain, combined with frequent droughts, make damaging floods much more likely.

You get this spiral downwards of vulnerability and destitution

John McGrath, Oxfam

The increasing number of weather events has been accompanied by large global population increases, and Oxfam says this means more people are being forced to live in areas which are vulnerable to the effects of the weather changes.

"They're going to forests, to jungles, to mountains... but these are just the very places that have been more affected by intense rain... and that in turn actually increases the displacement... so you get this spiral downwards of vulnerability and destitution," says Oxfam's John McGrath.

Unless the global aid community begins preparing for the future growth in weather-events, Oxfam warns, its ability to respond to natural disasters will be overwhelmed.